In all electronic equipment there is an electrical point connected to \u201cground\u201d. This grounding point may be a real connection to the mains ground or may be a \u201cvirtual ground\u201d, which is a relative internal grounding point, isolated from the external \u201cground\u201d. <\/p>\n
The ground potential is usually defined as a zero voltage potential, to which all voltages in the device are referenced. If two machines are connected, and they do not share the precise ground potential, \u201cground currents\u201d may flow from one machine to the other. In video equipment this creates a disturbance in the picture which is apparent as running bars on the screen or a snowy\/sparkly picture or an intermittent picture. In audio equipment it can cause a low frequency hum. In Hi-Fi audio equipment, accurate grounding within the machine is critical, as even a slight grounding issue can result in unsatisfactory performance. This problem is called a ground loop.<\/p>\n